Firefox 69: userChrome.css and userContent.css disabled by default

[harlan4096]

Mozilla plans to land a change in Firefox 69 that disables the loading of userChrome.css and userContent.css by default to improve performance.

The files userChrome.css and userContent.css are used to modify content of webpages or the browser itself using CSS instructions.

The option to do so is not removed but Mozilla plans to make it opt-in instead of opt-out. The organization states that not having to look for the two files on startup improves the start-up performance of the Firefox browser.

Firefox users who use the files already will have the feature enabled for them automatically to avoid disruptions to their workflows or expectations.

The preference needs to be flipped to True on new installations only starting with the release of Firefox 69.

Tip: check out customizing Firefox with userchrome.css.

Timeline for the change (proposed, subject to change):

* Firefox 68: Firefox checks if userChrome.css or userContent.css exist. If yes, preference will be set to True to allow the loading of these files on browser start. If no, preference remains set to False (don't look).

* Firefox 69: new installations will not support userChrome.css and userContent.css by default unless preference is set by the user.

Continue Reading